Fire refining of copper

ABSTRACT

A process is disclosed for fire-refining copper sulfide having a copper to nickel ratio of more than about 7:3, which process comprises maintaining a molten bath of copper sulfide in a turbulent state to volatilize at least about 50 percent of at least one impurity from the group consisting of bismuth, lead, tin and zinc, then surface blowing the turbulent bath of copper sulfide with a free-oxygen-containing gas to convert a minor portion of the copper sulfide to an immiscible metal phase in which at least one element from the group consisting of antimony, arsenic, bismuth, lead, tin and the precious metals is concentrated. After removing the immiscible metal phase the turbulent supernatant bath of copper sulfide is converted to liquid copper which is substantially saturated with oxygen by surface blowing with free oxygen-containing gas. At least one impurity from the group consisting of lead, selenium, sulfur, tellurium and tin are volatilized from the molten copper and the molten copper is thereafter treated with a reducing gas to lower the oxygen content to at least about 0.1 percent.

United States Patent 72] Inventors Paul E. Queneau [54] FIRE REFINING OFCOPPER 24 Claims, No Drawings [52] US. Cl 75/73, 75/82, 75/93 [51] Int.Cl ..C22bl5/06, C22b 23/06 [50] Field of Search 75/72, 1, 76, 83, 93

[56] References Cited UNITED STATES PATENTS 1,922,301 8/1933 Kekich75/75 2,790,713 4/1957 Kenworthy 75/82 2,944,883 7/1960 Queneau 75/82 X3,004,846 10/1961 Queneau 75/82 X 3,069,254 12/1962 Queneau 75/823,321,300 5/1967 Worner 75/93 X 3,516,818 6/1970 ONeill..... 75/74 X1,817,935 8/1931 Stout 75/76 2,758,022 B/1956 Jordon 75/76 OTHERREFERENCES Buch, I v E., The Mufulia Smelter, Northern Rhodesia in AIMETransactions, 1949, 182: p. 137 and 138.

Primary Examiner-L. Dewayne Rutledge Assistant Examiner-Joseph E. LegruAtt0rneyMaurice L. Pinel ABSTRACT: A process is disclosed forfire-refining copper sulfide having a copper to nickel ratio of morethan about 7:3, which process comprises maintaining a molten bath ofcopper sulfide in a turbulent state to volatilize at least about 50percent of at least one impurity from the group consisting of bismuth,lead, tin and zinc, then surface blowing the turbulent bath of coppersulfide with a free-oxygen-containing gas to convert a minor portion ofthe copper sulfide to an immiscible metal phase in which at least oneelement from the group consisting of antimony, arsenic, bismuth, lead,tin and the precious metals is concentrated. After removing theimmiscible metal phase the turbulent supernatant bath ofcopper sulfideis converted to liquid copper which is substantially saturated withoxygen by surface blowing with free oxygen-containing gas. At least oneimpurity from the group consisting of lead, selenium, sulfur, telluriumand tin are volatilized from the molten copper and the molten copper isthereafter treated with a reducing gas to lower the oxygen content to atleast about 0.1 percent.

FIRE REFllNllNG 01F COPPER The present invention relates to the firerefining of cupriferous materials to produce high-grade copper, and moreparticularly to an integrated process for treating copper sulfide whichmay contain nickel.

Production of refined copper from cupriferous. sulfidic materialsrequires a number of complex treatments involving high capitalexpenditures. Most of the virgin copper produced in the world isobtained by smelting copper sulfides in reverberatory or electricfurnaces, converting the resulting matte to blister copper in sideblownPeirce-Smith type converters, partially refining the blister copper bycrude redox operations in an anode furnace, casting the furnace productinto metal anodes, subjecting the anodes to electrolysis for finalrefining, melting the cathodes and casting the copper into shapes formarket. Fire refining of blister copper is also employed, which practiceinvolves an extension of anode furnace refining practice as a substitutefor electrolysis.

in addition to iron, sulfur and precious metals, containing furnace feedmay contain significant amounts of nickel originating in the ore or inscrap additions. Other common impurities which must be lowered toacceptable levels include antimony, arsenic, bismuth, lead, selenium,tellurium, tin and zinc. Prior art pyrometallurgical processes foreliminating such impurities from the final copper product are eitherinadequately effective or inefiicient.

It has now been discovered that cupriferous materials can be refinedpyrometallurgically to produce high grade copper while recoveringvaluable impurities by means of an economic, integrated process.

It is an object of the invention to provide a process forpyrometallurgical production of high-quality copper from cupriferousmaterials and for separate recovery of precious metals associatedtherewith.

Another object of the invention is to provide an integrated process forrecovering high-grade copper and nickel from copper sulfide containingnickel by a combination of pyrometallurgical and vapometallurgicaltechniques.

the copper- Generally speaking, the present invention contemplatesestablishing a turbulent bath containing copper sulfide and having acopper to nickel ratio of more than about 7:3, maintaining the bath in aturbulent state without forming a metal phase to volatilize more thanabout 50 percent of at least one impurity selected from the groupconsisting of bismuth, lead, tin and zinc, then surface blowing theturbulent bath with a free-oxygen-containing gas to convert a controlledminor portion of the copper sulfide to an immiscible metal phase inwhich at least one element from the group consisting of antimony,arsenic, bismuth, lead, tin and the precious metals is concentrated,removing the immiscible metal phase, then surface blowing the turbulentsupernatant bath of copper sulfide with a free-oxygen-containing gas toconvert copper sulfide to liquid copper, to substantially saturate theliquid copper with oxygen and to oxidize and volatilize at least oneimpurity selected from the group consisting of lead, selenium, sulfur,tellurium and tin and thereafter treating the liquid copper with anatmosphere reducing to cuprous oxide to lower the oxygen content to lessthan about 0.1 percent.

Copper mattes or copper sulfide concentrates which contain significantamounts of iron, nickel, cobalt, lead, bismuth, tin, arsenic, antimony,selenium, tellurium, zinc and the precious metals can be treated by theprocess of the present invention. Cupriferous scrap to which sufficientsulfur has been added to combine with all the copper contained thereincan also betreated in accordance with the present invention. It is to benoted that the term precious metals, as used herein, refers to theplatinum group metals and gold. When the feed material containssubstantial amounts of iron as iron sulfide, the iron is initiallyoxidized to iron oxide which is removed. The nickel content in thesulfide feed material must be controlled so that the copper to nickelratio is more than about 7:3 to insure production of the immiscibleliquid metal phase for the concentration of precious metals present andof impurities. Advantageously, the copper to nickel ratio in thecupriferous material is controlled at a level greater than about 10: 1since at ratios of copper to nickel of greater than about 10:] arsenic,in addition to bismuth, lead, tin and zinc, can be volatilized from boththe sulfide phase and the metal phase and the concentration of preciousmetals in the immiscible metalphase is remarkably more effective.Furthermore, at copper to nickel ratios of greater than about 10:],arsenic is more readily oxidized and volatilized from the liquid copperbath. Thus, control of the copper to nickel ratio at such levelsprovides more effective arsenic elimination and more effectiveconcentration of the precious metals in the immiscible metal phase. Whentreating sulfide mineral concentrates or metallurgical crudes thereofwhich have a copper to nickel ratio of less than about 10:1, suchmaterial can be treated to produce asulfur deficient matte, i.e., sulfurin amounts insufficient to form sulfides by combination with all of thenickel and copper. The matte of controlled sulfur content can then beslow cooled to provide a solidified mass of three readily separablephases-a precious-metals-containing magnetic fraction which is about 5percent to 15 percent of the solidified mass, a nickel sulfide fractionof low copper content and a copper sulfide fraction with a nickelcontent such that the copper to nickel ratio is greater than about 10:1,e.g., 15:1. This process for separation of nickel sulfide from coppersulfide isdescribed in Canadian Pat. Nos. 452,861 and 452,862. Theprecious-metals-containing magnetic fraction is ad vantageously melted,treated with. a free-oxygen-containing gas to lower the sulfur contentto between about 0.5 percent and 4 percent and the iron content to lessthanabout 3 percent, granulated by drastic quenching to uniformlydistribute the remaining sulfur throughout the granules and then treatedwith carbon monoxide at elevated pressure, advantageously below aboutatmospheres, to carbonylate and remove substantially all of the nickelas nickel carbonyl, as described in U.S. Pat. No. 1,067,638, leaving aresidue containing copper, sulfur and the precious metals which can betreated by leaching to remove copper, sulfur and other contaminants fromthe precious metals. Advantageously, the sulfur deficien cy of the matteis slight and is controlled so that only a nickel sulfide phasecontaining the precious metals and a copper sulfide phase are producedupon slow cooling. For example, the sulfur deficiency is controlled toproduce less than about 2 percent metallics, e.g., about 0.5 percent to1 percent metallics. The nickel sulfide phase is then treated in amanner similar to that described for the precious metals magneticfraction in order to concentrate the precious metals and to producenickel carbonyl. When the slow-cooled matte contains unimportant amountsof precious metals, the nickel sulfide fraction can advantageously beblown to nickel metal as described in Canadian Pat. No. 655,210. Thecopper sulfide fraction, with a copper to nickel ratio greater thanabout 10:1, can be treated in accordance with the process of the presentinvention.

An advantageous feature of the present invention is maintenance of aturbulent copper sulfide bath while avoiding formation of a metal phaseto maximize the volatilization of impurities from the liquid coppersulfide. Although some of the impurities are volatile as sulfides atconventional smelting and converting temperatures, the bath should beheld at temperatures above 1,300 C., more than about 1,400 C., in orderto increase the rate and the extent of impurity volatilization. Theresults shown in Table l, which were obtained by surface blowing coppermattes with air at temperatures of 1,200 and 1,340C. and with nitrogencontaining less than about 1 percent oxygen at a temperature of 1,500"C. for one hour, confirm that higher temperatures are more effective involatilizing impurities such as bismuth and lead from the matte. Thiscomparison must take into consideration the loss of weight of the mattebeing treated. The effectiveness of higher smelting and convertingtemperatures is confirmed by the results in table 11 from which it isreadily seen that surface blowing with air at higher temperatures givesa remarkable decrease in the level of impuriadvantageously attemperatures of ties commonly present in smelter feed. It is importantduring this phase of the treatment to avoid formation of a metal phasesince such a phase tends to preferentially dissolve the impurities,which dissolution sharply lowers impurity volatilization efficiency.Advantageously, this part of the process is conducted in a top-blownrotary converter, e.g., a Kaldo converter, equipped with a burner, whichconverter provides great flexibility in operation by provision ofgaseous atmospheres of optimum oxidizing potential, independent controlof bath temperature and independent mechanical generation of a turbulentbath for excellent gas-liquid-solid contact. The absence of submergedtuyeres in such converters allows them to be operated at hightemperatures unattainable in the standard converters of the nonferrousindustry. When the sulfide bath is a low-grade matte, some of theimpurities can be volatilized during the oxidation and slagging of iron.However, when the sulfide bath is a high-grade matte, impurities such asarsenic, bismuth, lead, tin and zinc are advantageously volatilized bymaintaining the copper-containing sulfide bath in a turbulent state byeither pneumatic or mechanical means and without forming a metal phaseby maintaining high temperature, neutral or only slightly oxidizingatmospheres above the turbulent bath. For example, surface blowing apartially converted matte at 1,340 C. with nitrogen containing less thanabout 1 percent oxygen, by volume, was effective in lowering the lead,arsenic and bismuth contents as shown in table Ill. The results in tablelll also confirm that superior results are obtained by volatilizingimpurities from the matte at temperatures above 1,400 C. The testconducted at 1,500 C. employed surface blowing with air for the first 10minutes, then surface blowing with nitrogen containing less than about 1percent oxygen, by volume, for the remainder of the test. It is readilyapparent from the results in table 111 that temperatures above 1,400" C.are effective in increasing the rate and extent of impurity eliminationfrom the matte phase. The latter embodiment is advantageously conductedin a top blown converter with the burner being operated to maintain bothhigh bath temperature and an atmosphere substantially neutral to coppersulfide, i.e., neither oxidizing nor reducing to copper sulfide.Advantageously, the atmosphere above the sulfide bath is controlled tohave an oxidizing-reducing potential equivalent to a value between about10 1 and 10 for the ratio of (CO)(SO )%(CO wherein the values of CO, 50and CO are their respective partial pressures. Both the rate and extentof impurity volatilization from the matte can advantageously be improvedby subjecting the matte, after iron removal, to a subatmosphericpressure treatment. The matte is advantageously transferred to aseparate vessel wherein it is maintained in a turbulent state and athigh temperatures, e.g., above l,400 C., and the pressure in the vesselis lowered to less than about 10 atmosphere.

TABLE I Temper- Perccnt ature, M Sample C. Cu S Fe Bi Pb HeatL 1,500 4825 20.5 0.05 116 After 1 hour 1,500 21. 5 0. 026 0 058 Head 1, 340 4225. 9 28 0. 11 0. 13 After 1 hour 1,340 53. 5 24 10. 5 0.07 0.11 H 1,20041.9 26 28.3 0.11 0.13 After 1 hour 1,200 57. 4 23. 7 14. 7 0. 11 0. 14

1 Not analyzed.

TABLE II Temper- Percent ature,

Sample 0, Cu Se Fe As Bi Pb Head 1,340 42 0.1 28. 5 0.11 0.11 0. 13Blister 1, 340 0. 003 0. 03 0. 44 0. 002 Head 1, 200 41. 9 0.104 28. 30.11 0.11 0.13 Blister. 1,200 0.02 0.07 0.18 0. 006

l Contained about 26% sulfur. 2 Balance includes small amounts of iron,sulfur and oxygen. 3 Not analyzed.

TABLE III Temper- Percent ature, M Sample C. Fe Pb As Bi Partiallyconverted matte 1, 340 10 0. 092 0. 012 0. 05 After blowing:

hour 1, 340 18 0. 083 0. 013 0. 03 1 hour 1, 340 15 0. 064 0. 012 0. 012 hour 1, 340 10 0. 054 0. 011 0. 01 Head 1, 500 20. 5 0. 096 0. 09 0.075 Alter blow hour. 1, 500 21. 5 0. 072 0. 05 0. 035 1 hour. 1, 500 21.5 0. 058 0. 04 0. 026 1% hours. 1, 500 21. 0 0. 054 0. 035 0. 01 2hours- 1,500 20. 5 0. 053 0. 031 0. 01 solidified sample 17. 5 0. 048 0.027 0. 01

After the copper-containing sulfide feed has been melted, iron presenthas been oxidized by blowing and removed and substantial amounts ofimpurities such as arsenic, bismuth, lead, tin and zinc have beenvolatilized, the turbulent sulfide bath is surface blown withfree-oxygen-containing gas, such as air, oxygen-enriched air ofcommercial oxygen, to convert a controlled portion of the sulfide bathinto a metal phase to collect substantially all the precious metals andsubstantial portions of other impurities remaining in the bath.Advantageously, the metallized portion of the bath is controlled withinthe limits of about 5 percent to about 15 percent of the sulfide phase,by weight, to insure collection of the precious metals and concentrationof substantial portions of other impurities. It will be noted here thata highly desirable combination exists between the elimination of theimpurities from the matte by volatilization and the subsequentcollection of impurities and precious metals in the immiscible moltenmetal phase. Since more than about 50 percent of at least one impurityfrom the group consisting of arsenic, bismuth, lead, tin and zinc isremoved by volatilization from the sulfide phase, a smaller amount ofthe immiscible metal phase can be formed and later tapped to removeremaining impurities and, therefore, the latter step is economicallyadvantageous. Greater and lesser amounts of the metal phase can beemployed but greater amounts, unless warranted by the precious metalcontent, result in a less economical process while lesser amounts resultin substantially lower collection of the precious metals and theimpurities. in order to confirm the effectiveness of a metal phase inconcentrating impurities, a test, the results of which are shown intable IV, was conducted on a copper matte which was surface blown withair at l,340 C. to produce a metal phase which was about 10 percent, byweight, of the matte phase. The results in table lV show thatconcentrations of impurities in the metal phase are at minimum fivetimes greater than in the matte phase and even 10 times or more. It willalso be noted from table N that antimony, which is particularlydifficult to eliminate by volatilization from the sulfide phase or bysubsequent oxidation and volatilization from the metal phase, is highlyconcentrated and collected in the metal phase. Thus, substantial amountsof antimony can be eliminated at this point in the process withoutemploying special slagging techniques at later processing stages. Strongagitation of the sulfide bath to insure efiective interphaseliquid-liquid contact and resulting washing of the sulfide phase by themetal phase is important at this point to collect precious metals andother impurities in the metal phase. The metal is then allowed to settleinto a liquid bottom and is removed for treatment, e.g., cast intoanodes and treated electrolytically to recover the copper and theprecious metals.

It has been found that the embodiments of volatilizing impurities fromthe sulfide phase and of concentrating the precious metals andimpurities are dependent on the copper to nickel ratios in the sulfidematerial being treated and that for the greatest efficiency of bothembodiments the copper to nickel ratio should be morethan about :1.Although applicants do not wish to be bound by any particular theory, itis believed that increasing amounts of nickel in the sulfide phase lowerthe chemical activities of the precious metals and impurities in thesulfide phase. Whatever the explanation for the adverse effects ofexcessive amounts of nickel in the sulfide phase, tests have shown thatit is advantageous to control the copper to nickel ratio to a value ofmore than about 10:]. Thus, a copper matte containing 42 percent copper,28.5 percent iron, 25.9 percent sulfur, 0.11 percent arsenic and thebalance essentially silica was surface blown with air at a temperatureof 1,340 C. for 1 hour to lower the sulfur content to 24 percent, theiron content to 19.5 percent and the arsenic content to 0.035 percent.In a similar manner, a matte containing 29.4 percent copper, 13.9percent nickel, 27.6 percent iron, 26 percent sulfur, 0.103 percentarsenic and the balance essentially silica was surface blown with air ata temperature of l,340 C. for about 100 minutes to lower the ironcontent to l 1 percent, the sulfur content to 24.5 percent and thearsenic content to about 0.088 percent. Thus, it is seen from the firsttest that the proportion of arsenic in the matte was lowered by morethan two-thirds when no nickel was present while in the second test witha copper to nickel ratio of 2.1:] the proportion of arsenic in the mattewas lowered by less than about percent. In addition to lowering theefficiency of arsenic volatilization from the matte, excessive amountsof nickel in the matte also lower the efficiency of precious metalconcentration in the immiscible metal phase. For example, in two testsin which the copper to nickel ratios were 13:1 and 5:1 the overalldistribution of precious metals in the metal phase was as follows:

TABLE V Percentage of Total Precious Metals in Metal Phase Cu2Ni 1' ofPd of Pt it of Au The results in table 1V confirm the importance ofcontrolling the copper to nickel ratio to have a value of more thanabout 10:1.

The partially purified copper sulfide remaining in the converter, e.g.,a Kaldo or LD converter, is maintained in a state of turbulence, bymechanical or pneumatic means, as top blowing with afree-oxygen-containing gas such as air, commercial oxygen oroxygen-enriched air is resumed. Surface blowing is continued to convertthe partially purified copper sulfide to copper and to substantiallysaturate the copper with cuprous oxide, e.g., an oxygen content ofbetween about 0.5 percent and 1.5 percent. During this stage of theblowing operation, the surface of the turbulent liquid bath is keptreasonably clear of slag in order to assure efficient gas-liquid contactand the bath is maintained at a temperature between about l,l00 andl,500 C. The introduction of the aforementioned amounts of oxygen iseffective in oxidizing the impurities remaining in the liquid copperbath and in volatilizing more than about 50 percent of at least onevolatile oxide of elements such as arsenic, lead, selenium, sulfur,tellurium and tin. Advantageously, the oxidation and volatilization ofthe impurities is conducted at temperatures above l,300 C. in order toinsure more rapid and complete elimination of the impurities. The oxygencontained in the copper bath is also effective in oxidizingsubstantially all of the nickel in the bath. Nickel removal isadvantageously conducted at low temperatures, e.g., about l,l00 C.,because at higher temperatures nickel removal is less efficient.Although the nickel content can be lowered to below 0.5 percent withouta flux at a temperature of about l,l00 C., the nickel content can befurther lowered by employing an acidic flux such as silica. When anacidic flux is employed, the nickel content in the copper bath can belowered to about 0.1 percent,

After such purification, the copper-containing bath is then brought tothe proper pitch and cast. Advantageously, the purified liquidcopper-containing bath containing up to about 1.5 percent oxygen istreated with an atmosphere reducing to cuprous oxide to lower the oxygencontent to less than about 0.1 percent. In bringing the moltencopper-containing bath to the proper pitch, the bath is held at atemperature of about 1,100 to about l,200 C. while maintaining theatmosphere above the bath to have a reducing potential equivalent to aCOzCO ratio of at least one part of CO for each 1,000 parts of CO Forkinetic reasons, it is advantageous to employ atmospheres havingreducing potentials equivalent to COzCO ratios of at least about 1:50,e.g., about 1:10. To facilitate lowering of the oxygen content in thesecond reaction vessel, a turbulent bath is also employed therein inorder to assure intimate gas-liquid contact. Alternatively, the oxygencontent of the copper bath can be lowered during the subatmosphericpressure treatment described hereinafter by passing reducing gaseshaving the aforedescribed reducing potentials through the copper bath.When the oxygen content has been lowered to predetermined levels, thecopper-containing bath is cast into commercial shapes such as wire barsor cast into anodes for further purification.

If it is desired to continuously cast the copper-containing bath or if aproduct substantially free of gas is desired, the copper-containing bathis advantageously subjected to a subatmospheric pressure treatment todegas the bath. The copper-containing bath is introduced to a vacuumchamber which is maintained at a pressure of less than about 10atmosphere. The subatmospheric pressure treatment will be more efficientif the copper-containing bath is maintained in constant state ofcirculation or turbulence by well-known means, e.g., electromechanical.In addition to the degassing effect, the subatmospheric pressuretreatment has the further advantage of further lowering the level ofimpurities such as sulfur, arsenic, bismuth, lead, selenium, sulfur,tellurium, tin and zinc by volatilization. The effectiveness of thesubatmospheric pressure treatment in lowering the level of the variousimpurities is partly dependent on the oxygen content of the liquidcopper. For example, the lead content can be lowered in the absence ofoxygen but the elimination of sulfur and arsenic is facilitated by thepresence of sufficient oxygen as cuprous oxide to form the volatileoxides of the respective impurities. In order to insure elimination ofsulfur and/or arsenic, the copper-containing bath with oxygen contentsup to about 1.5 percent can be directly transferred to the vacuumchamber without deoxidation; and after these impurities have beenlowered to acceptable levels, reducing gases having a reducing potentialequivalent to COzCO ratios of at least one part of CO for each 1,000parts ofCO are then passed through the liquid copper. Although thesubatmospheric pressure treatment is effective in lowering the impuritylevels at conventionally employed temperatures for casting copper, ithas been found particularly advantageous to subject the copper bath tothe subatmospheric pressure treatment at temperatures of at least about1,200 C. Even bismuth, which is considered difficult or impossible toeliminate by conventional pyrometallurgical techniques, can be readilyremoved by the subatmospheric pressure treatment. In a test, a sample ofcopper containing 20 parts per million (ppm) bismuth was heated to aboutl,l50 C. for 45 minutes at a final vacuum of 14 microns and the bismuthcontent was lowered to less than 1 ppm. The results in table Vl furtherconfirm the effectiveness of the subatmospheric pressure treatment inlowering the impurity levels. The results shown in table Vl wereobtained by subjecting molten copper containing about 0.3 percent oxygento a subatmospheric pressure of 0.4x 1 0 atmosphere for 1 /2 hours at atemperature of 1,260 C. It is quite evident from the results in table Vlthat the subatmospheric pressure treatment is highly effective inremoving lead, arsenic and bismuth.

n.d.= not detected For the purpose of giving those skilled in the art abetter appreciation of the advantages of this invention, the followingillustrative example is given:

EXAMPLE I A turbulent bath of copper matte, the composition of which isgiven in table Vll, was established and surface blown with oxygen for 1%hours at l,340 C. and then a sample was taken for analysis. Surfaceblowing of the turbulent bath with oxygen was then discontinued and wasreplaced by surface blowing with nitrogen containing less than about 1percent oxygen for 2 hours at l,340 C. after which a sample was takenfor analysis. Surface blowing of the turbulent bath with oxygen at l,340C. was resumed for 1 hour to produce a metal phase which, along with asample of matte, was removed and analyzed. After 70 minutes of surfaceblowing with oxygen at 1,340 C. another metal phase was produced and wasagain removed along with a sample of the matte for analysis. Theremaining matte was converted to blister copper and saturated withoxygen after blowing with oxygen for 80 minutes. After taking twosamples for analysis, the blister copper was subjected to asubatmospheric pressure of less than about 1O atmosphere at 1,500 C. Theresults of the chemical analyses at different stages of the process arereported in table Vll together with an analysis of commercially producedcathode copper for comparative purposes. The results in table Vllconfirm that copper produced in accordance with the process of thepresent invention is comparable with electrolytic copper. In addition tothe results listed in table VII, the tellurium content, which was 0.lpercent in the head sample, was lowered to less than 0.01 percent afterthe vacuum treatment whereas a similar vacuum treatment at l,260 C. onlylowered the tellurium content to 0.05 percent. Also, one of the blistercopper samples contained 0.3 percent selenium; and after the vacuumtreatment at 1,500 C., the selenium content was lowered to less thanabout 0.002 percent.

lence can be induced by pneumatic or electromagnetic means. Theefficiency of volatilizing impurities from the matte is greatlyincreased by a turbulent bath since the turbulence constantly exposesfresh surfaces from which volatilization occurs. The use of a rotaryfurnace during the converting operation is advantageous since therotating furnace avoids the establishment of localized areas of lowertemperature where magnetite and other accretions can build up andeventually lower the capacity of the converter. Furthermore, theturbulence induced by a rotary converter provides a rapid approach toequilibrium conditions by rapid decrease of concentration gradients and,thus, for instance, the problem of slag foaming is minimized. Theturbulence mechanically induced by a rotary furnace also providesexcellent liquid-liquid contact between the impure copper sulfide phaseand the controlled metal portion, which contact greatly increases theamount and rate of concentration of impurities in the controlled metalportion. The highly efficient gas-liquid contact realized by conductingthe process in a top blown furnace provides greater control of theproduction of the controlled metal portion, the converting of thepartially purified copper sulfide and the subsequent oxidation of theremaining impurities in the coppercontaining bath. A rotary furnacepermits required tempera ture control including efficient heat exchangebetween the liquid bath and the furnace wall refractory. The furnace isequipped with a lance for delivering freeoxygen-containing gas tothe'surface of the turbulent bath and with a burner for supplying heatto, and for controlling the atmosphere above, the turbulent bath. Theburner gases serve the additional function of continually flowing overthe surface of the turbulent bath thereby flushing residual gases andlowering the partial pressures of volatile impurities wherebyvolatilization efficiency is increased.

Top blowing by directing a stream of free-oxygen-containing gas on thesurface of the agitated bath is another advantageous feature of thepresent invention. When a free-oxygen-containing gas is directed to thesurface of a molten copper-containing sulfide bath, liquid copper isformed in the vicinity of impingement of the free-oxygcn-containing gasand by gravitational forces descends through the molten sulfide phasewhich provides even greater liquid-liquid contact between the liquidsulfide phase and the liquid copper to further increase theeffectiveness of the concentration of impurities in the liquid copper.it is to be further noted that the surface blowing permits the use ofcommercial oxygen or oxygen-enriched air during the converting operationwhereby the offgases are rich in sulfur dioxide which facilitates sulfurrecovery. Surface blowing is also characterized by a high oxygenactivity which in combination with independent agitation by mechanicalmeans and independent temperature control provides procedures responsiveto accurate regulation of TABLE VII Percent- Weight Tempera- (grams)ture, 0. Fe Pb As Bi S 1, 340 1.17 2 0.007 0.012 Metal 1, 340 0. 01 2 0.003 0. 03 Blow 02.80 minutes 1,340 0.03 2 0. 0006 1 0.005 1, 340 0.020.0013 0.0001 2 0. 005 0. 005 Vacuum 1, 500 0. 01 0. 001 0.001 0. 00010. 001 0. 0001 0. 002 1,500 0. 01 0. 001 0. 001 0. 0001 0. 001 0. 00010. 002 Cathode copper t t 0.0005 0. 0001 0.0001 0. 0003 0.0001 0. 00010. 0005 Not analyzed. 2 Speetrographically estimated.

A turbulent bath is one of the advantageous features of the processvariables.

present invention and is achieved advantageously by the mechanicallyinduced agitation of a rotary furnace of the Kaldo type because therotary furnace provides agitation independent of any other function.Although the mechanically induced agitation of a rotary furnace ispreferred, the turbu- It will be observed that the present inventioncontemplates, in an advantageous embodiment, establishing a turbulentbath containing copper sulfide and having a copper to nickel ratio ofmore than about 10:1, maintaining the bath in a turbulent state withoutforming a metal phase to volatilize more than about 50 percent of atleast one impurity selected from the group consisting of arsenic,bismuth, lead, tin and zinc, then surface blowing the turbulent bathwith a free-oxygen-containing gas to convert a controlled minor portionof the copper sulfide to an immiscible metal phase in which at least oneelement from the group consisting of antimony, arsenic, bismuth, lead,tin and the precious metals is concentrated, removing the immisciblemetal phase, then surface blowing the turbulent supernatant bath ofcopper sulfide with a free-oxygencontaining gas to convert coppersulfide to a turbulent bath of liquid copper, to substantially saturatethe liquid copper with oxygen and to oxidize and volatilize at least oneimpurity selected from the group consisting of arsenic, lead, selenium,sulfur, tellurium and tin and thereafter treating the liquid copper withan atmosphere reducing to cuprous oxide to lower the oxygen content toless than about O. l percent.

It is to be noted that all solid and liquid composition given herein aretaken on a weight basis and that all gaseous compositions are given on avolumetric basis.

Although the present invention has been described in conjunction withpreferred embodiments, it is to be understood that modifications andvariations may be resorted to without departing from the spirit andscope of the invention, as those skilled in the art will readilyunderstand. Thus, the process in accordance with the present invention,particularly the use of a turbulent bath, can be employed for thetreatment of plumbiferous materials, e.g. mineral concentrates, to yielddirectly fire-refined lead. Such modifications and variations areconsidered to be within the purview and scope of the invention andappended claims.

We claim:

1. A method for recovering copper from cupriferous materials whichcomprises establishing a bath containing copper sulfide and having acopper to nickel ratio of more than about 7:3, maintaining said bathcontaining copper sulfide in a turbulent state without forming a metalphase to volatilize more than about 50 percent of at least one impurityselected from the group consisting of bismuth, lead, tin and zinc, thensurface blowing the turbulent bath containing copper sulfide with afree-oxygen-containing gas to convert a controlled minor portion of thecopper sulfide to an immiscible metal phase in which at least oneelement from the group consisting of antimony, arsenic, bismuth, lead,tin and the precious metals is concentrated, removing the immisciblemetal phase, then surface blowing the turbulent supernatant coppersulfide with a free-oxygen-containing gas to convert copper sulfide toliquid copper, to substantially saturate the liquid copper with oxygenand to oxidize and volatilize at least one impurity from the groupconsisting of lead, selenium, sulfur, tellurium and tin and thentreating the liquid copper with an atmosphere reducing to cuprous oxideto lower the oxygen content to less than about O.l percent.

2. A method for recovering copper from cupriferous materials whichcomprises establishing a bath containing copper sulfide and having acopper to nickel ratio of more than about 10:1, maintaining said bathcontaining copper sulfide in a turbulent state without forming a metalphase to volatilize more than about 50 percent of at least one impurityselected from the group consisting of arsenic, bismuth, lead, tin andzinc, then surface blowing the turbulent bath containing copper sulfidewith a free-oxygen'containing gas to convert a controlled minor portionof the copper sulfide to an immiscible metal phase in which at least oneelement from the group consisting of antimony, arsenic, bismuth, lead,tin and the precious metals is concentrated, removing the immisciblemetal phase, then surface blowing the turbulent supernatant bath ofcopper sulfide with a free-oxygen-containing gas to convert coppersulfide to liquid copper, to substantially saturate the liquid copperwith oxygen and to oxidize and volatilize at least one impurity from thegroup consisting of arsenic, lead, selenium, sulfur, tellurium and tinand then treating the liquid copper with an atmosphere reducing tocuprous oxide to lower the oxygen content to less than about 0.1percent.

comprises establishing a turbulent bath of a sulfide material containingnickel, copper and the precious metals with the copper to nickel ratiobeing less than about 10:1, directing a stream of afree-oxygen-containing gas upon the surface of the turbulent bath toproduce a sulfur-deficient matte, slowly cooling the sulfur-deficientmatte to produce a solidified mass of readily separable crystals ofnickel sulfide and copper sulfide having a copper to nickel ratiogreater than about l'0:l and a magnetic metallic fraction in which thepreciousmetals are concentrated, comminuting the solidified mass,magnetically separating the metallic fraction, separating the nickelsulfide and copper sulfide by flotation, melting and then surfaceblowing the separated metallic fraction with a free-oxygen-containinggas to produce a molten nickel bath containing about 0.5 percent toabout 4 percent sulfur and less than about 3 percent iron, drasticallyquenching the nickel bath to form nickel granules with sulfur uniformlydistributed, carbonylating the nickel granules at elevated pressures toproduce nickel carbonyl and a precious metal concentrate, fire refiningthe separated nickel sulfide by surface blowing a turbulent bath thereofwith a free-oxygen-containing gas, establishing a bath of the separatedcopper sulfide, maintaining said bath containing copper sulfide in aturbulent state without forming a metal phase to volatilize more thanabout 50 percent of at least one impurity selected from the groupconsisting of arsenic, bismuth, lead, tin and zinc, then surface blowingthe turbulent bath containing copper sulfide with afree-oxygen-containing gas to convert a controlled portion of the coppersulfide to an immiscible metal phase in which at least one element fromthe group consisting of antimony, arsenic, bismuth, lead, tin and theprecious metals is concentrated, removing the. immiscible metal phase,then surface blowing the turbulent supernatant bath of copper sulfidewith a free-oxygen-containing gas to convert copper sulfide to liquidcopper, to substantially saturate the liquid copper with oxygen and tooxidize and volatilize at least one impurity from the group consistingof arsenic, lead, selenium, sulfur, tellurium and tin and then treatingthe liquid copper with an atmospherp reducing to cuprous oxide to lowerthe oxygen content to less than about 0.1 percent.

4. A process for recovering copper, nickel and precious metals fromnickeland copper-containing materials which comprises establishing aturbulent molten bath of a sulfide material, directing a stream of afree-oxygen-containing gas upon the surface of the turbulent bath toproduce a sulfur deficient matte, slowly cooling the sulfur deficientmatte to produce a solidified mass of readily separable crystals ofnickel sulfide which contains precious metals and copper sulfidecrystals having a copper to nickel ratio greater than about 10:1,comminuting the solidified mass, separating the nickel sulfide andcopper sulfide phases in the comminuted mass by flotation, melting andthen surface blowing the nickel sulfide phase to produce a nickel bathcontaining about 0.5 percent to about t percent sulfur and less thanabout 3 percent iron, drastically quenching the nickel bath to formnickel granules with sulfur uniformly distributed, carbonylating thenickel granules at elevated pressures to produce nickel carbonyl and aprecious metal concentrate, establishing a turbulent bath of theseparated copper sulfide, maintaining said bath containing coppersulfide in -a turbulent state without forming a metal phase tovolatilize more than about 5 0 percent of at least one impurity selectedfrom the group consisting of arsenic, bismuth, lead, tin and zinc, thensurface blowing the turbulent bath containing copper sulfide with afree-oxygen-containing gas to convert a controlled portion of the coppersulfide to an immiscible metal phase in which at least one element fromthe group consisting of antimony, arsenic, bismuth, lead, tin and theprecious metals is concentrated, removing the immiscible metal phase,then surface blowing the supernatant turbulent bath of. copper sulfidewith a free-oxygen-containing gas to convert copper sulfide to liquidcopper, to substantially saturate the liquid copper with oxygen and tooxidize and volatilize at least one impurity from the group consistingof arsenic, lead, selenium, sulfur, tellurium and tin and then treatingthe liquid copper with an atmosphere reducing to cuprous oxide to lowerthe oxygen content to less than about 0.1 percent.

5. A process as described in claim 2 wherein the impurities arevolatilized from the bath containing copper sulfide at a temperatureabove 1,300 C.

6. A process as described in claim 2 wherein the impurities arevolatilized from the bath containing copper sulfide at a temperature ofmore than 1,400 C.

7. A process as described in claim 2 wherein the molten bath containingcopper sulfide is a low-grade matte and the impurities are volatilizedwhile surface blowing the turbulent bath with a free-oxygen-containinggas.

8. A process as described in claim 2 wherein the coppersulfide-containing bath is a high-grade matte and the impurities arevolatilized by controlling the atmosphere above the turbulent bath to besubstantially neutral to copper sulfide.

9. A process as described in claim 8 wherein the atmosphere above thebath is controlled to have an oxidizing-reducing potential equivalent toa value between about 10 and 10 for the ratio (CO)(SO,)%(CO,) whereinthe values of CO, S and CO are the respective partial pressures.

10. A process as described in claim 3 wherein impurities are volatilizedfrom the copper sulfide-containing bath by maintaining the atmosphereabove the turbulent bath to be substantially neutral to copper sulfide.

11. A process as described in claim wherein the atmosphere above thebath is controlled to have an oxidizingreducing potential equivalent toa value between about 10 and 10 for the ratio (CO)(SO,)%(CO wherein thevalues of CO, S0 and C0: are the respective partial pressures.

12. A process as described in claim 2 wherein the immiscible metal phaseis from about 5 percent to about percent, by weight, of the moltencopper sulfide.

13. A process as described wherein more than about 50 percent of atleast one impurity from the group consisting of arsenic, lead, selenium,sulfur, tellurium and tin is volatilized from the liquid copper bathsubstantially saturated with oxygen.

14. A process as described in claim 2 wherein the liquid bath of coppersubstantially saturated with oxygen is treated with an atmosphere havinga reducing potential equivalent to a CO:CO, ratio of at least about1:1000 to lower the oxygen content to less than about 0.1 percent.

15. A process as described in claim 14 wherein the atmosphere has areducing potential equivalent to a CO:CO, ratio of at least about 1:5

16.'A process as described in claim 2 wherein the liquid coppercontaining less than about 0.1 percent oxygen is degassed and furtherpurified by a subatmospheric pressure treatment.

17. A process as described in claim 16 wherein after degassing theliquid copper is continuously cast.

18. A process as described in claim 2 wherein the liquid coppersubstantially saturated with oxygen is subjected to a subatmosphericpreaure treatment to further lower the level of at least one impurityselected from the group consisting of arsenic, bismuth, lead, selenium,sulfur, tellurium, tin and zinc before treating the liquidcopper with anatmosphere reducing to cuprous oxide.

19. A process as described in claim 18 wherein an atmosphere reducing tocuprous oxide is passed through the liquid copper during thesubatmospheric pressure treatment to lower the oxygen content in themolten copper to less than about 0.1 percent.

20. A process as described in claim 18 wherein the subatmosphericpressure is less than about 10' atmosphere.

21. A process as described in claim 2 wherein the steps ofvolatilization of impurities from the copper sulfide-containing bath,the production of the controlled amount of immiscible molten metal phaseand the converting of the copper sulfide to a molten bath of copger areconducted in a rotary furnace.

22. A process as escribed in claim 2 wherein the step of volatilizationof impurities from the copper sulfide-containing bath is conducted atsubatmospheric pressures of less than about 10" atmosphere.

23. A process as described in claim 3 wherein the precious metalconcentrate from the carbonylation treatment is leached to furtherconcentrate the precious metals by removing copper, sulfur and othercontaminants.

24. A process as described in claim 3 wherein the elevated pressureduring carbonylation is less than about 100 atmospheres.

2. A method for recovering copper from cupriferous materials whichcomprises establishing a bath containing copper sulfide and having acopper to nickel ratio oF more than about 10:1, maintaining said bathcontaining copper sulfide in a turbulent state without forming a metalphase to volatilize more than about 50 percent of at least one impurityselected from the group consisting of arsenic, bismuth, lead, tin andzinc, then surface blowing the turbulent bath containing copper sulfidewith a free-oxygen-containing gas to convert a controlled minor portionof the copper sulfide to an immiscible metal phase in which at least oneelement from the group consisting of antimony, arsenic, bismuth, lead,tin and the precious metals is concentrated, removing the immisciblemetal phase, then surface blowing the turbulent supernatant bath ofcopper sulfide with a free-oxygen-containing gas to convert coppersulfide to liquid copper, to substantially saturate the liquid copperwith oxygen and to oxidize and volatilize at least one impurity from thegroup consisting of arsenic, lead, selenium, sulfur, tellurium and tinand then treating the liquid copper with an atmosphere reducing tocuprous oxide to lower the oxygen content to less than about 0.1percent.
 3. A process for recovering copper, nickel and precious metalsfrom nickel and copper-containing materials which comprises establishinga turbulent bath of a sulfide material containing nickel, copper and theprecious metals with the copper to nickel ratio being less than about10:1, directing a stream of a free-oxygen-containing gas upon thesurface of the turbulent bath to produce a sulfur-deficient matte,slowly cooling the sulfur-deficient matte to produce a solidified massof readily separable crystals of nickel sulfide and copper sulfidehaving a copper to nickel ratio greater than about 10:1 and a magneticmetallic fraction in which the precious metals are concentrated,comminuting the solidified mass, magnetically separating the metallicfraction, separating the nickel sulfide and copper sulfide by flotation,melting and then surface blowing the separated metallic fraction with afree-oxygen-containing gas to produce a molten nickel bath containingabout 0.5 percent to about 4 percent sulfur and less than about 3percent iron, drastically quenching the nickel bath to form nickelgranules with sulfur uniformly distributed, carbonylating the nickelgranules at elevated pressures to produce nickel carbonyl and a preciousmetal concentrate, fire refining the separated nickel sulfide by surfaceblowing a turbulent bath thereof with a free-oxygen-containing gas,establishing a bath of the separated copper sulfide, maintaining saidbath containing copper sulfide in a turbulent state without forming ametal phase to volatilize more than about 50 percent of at least oneimpurity selected from the group consisting of arsenic, bismuth, lead,tin and zinc, then surface blowing the turbulent bath containing coppersulfide with a free-oxygen-containing gas to convert a controlledportion of the copper sulfide to an immiscible metal phase in which atleast one element from the group consisting of antimony, arsenic,bismuth, lead, tin and the precious metals is concentrated, removing theimmiscible metal phase, then surface blowing the turbulent supernatantbath of copper sulfide with a free-oxygen-containing gas to convertcopper sulfide to liquid copper, to substantially saturate the liquidcopper with oxygen and to oxidize and volatilize at least one impurityfrom the group consisting of arsenic, lead, selenium, sulfur, telluriumand tin and then treating the liquid copper with an atmosphere reducingto cuprous oxide to lower the oxygen content to less than about 0.1percent.
 4. A process for recovering copper, nickel and precious metalsfrom nickel- and copper-containing materials which comprisesestablishing a turbulent molten bath of a sulfide material, directing astream of a free-oxygen-containing gas upon the surface of the turbulentbath to produce a sulfur deficient matte, slowly cooling the sulfurdeficient matte to produCe a solidified mass of readily separablecrystals of nickel sulfide which contains precious metals and coppersulfide crystals having a copper to nickel ratio greater than about10:1, comminuting the solidified mass, separating the nickel sulfide andcopper sulfide phases in the comminuted mass by flotation, melting andthen surface blowing the nickel sulfide phase to produce a nickel bathcontaining about 0.5 percent to about 4 percent sulfur and less thanabout 3 percent iron, drastically quenching the nickel bath to formnickel granules with sulfur uniformly distributed, carbonylating thenickel granules at elevated pressures to produce nickel carbonyl and aprecious metal concentrate, establishing a turbulent bath of theseparated copper sulfide, maintaining said bath containing coppersulfide in a turbulent state without forming a metal phase to volatilizemore than about 50 percent of at least one impurity selected from thegroup consisting of arsenic, bismuth, lead, tin and zinc, then surfaceblowing the turbulent bath containing copper sulfide with afree-oxygen-containing gas to convert a controlled portion of the coppersulfide to an immiscible metal phase in which at least one element fromthe group consisting of antimony, arsenic, bismuth, lead, tin and theprecious metals is concentrated, removing the immiscible metal phase,then surface blowing the supernatant turbulent bath of copper sulfidewith a free-oxygen-containing gas to convert copper sulfide to liquidcopper, to substantially saturate the liquid copper with oxygen and tooxidize and volatilize at least one impurity from the group consistingof arsenic, lead, selenium, sulfur, tellurium and tin and then treatingthe liquid copper with an atmosphere reducing to cuprous oxide to lowerthe oxygen content to less than about 0.1 percent.
 5. A process asdescribed in claim 2 wherein the impurities are volatilized from thebath containing copper sulfide at a temperature above 1,300* C.
 6. Aprocess as described in claim 2 wherein the impurities are volatilizedfrom the bath containing copper sulfide at a temperature of more than1,400* C.
 7. A process as described in claim 2 wherein the molten bathcontaining copper sulfide is a low-grade matte and the impurities arevolatilized while surface blowing the turbulent bath with afree-oxygen-containing gas.
 8. A process as described in claim 2 whereinthe copper sulfide-containing bath is a high-grade matte and theimpurities are volatilized by controlling the atmosphere above theturbulent bath to be substantially neutral to copper sulfide.
 9. Aprocess as described in claim 8 wherein the atmosphere above the bath iscontrolled to have an oxidizing-reducing potential equivalent to a valuebetween about 10 1 and 10 4 for the ratio (CO)(SO2) 1/2 (CO2) 1 whereinthe values of CO, SO2 and CO2 are the respective partial pressures. 10.A process as described in claim 3 wherein impurities are volatilizedfrom the copper sulfide-containing bath by maintaining the atmosphereabove the turbulent bath to be substantially neutral to copper sulfide.11. A process as described in claim 10 wherein the atmosphere above thebath is controlled to have an oxidizing-reducing potential equivalent toa value between about 10 1 and 10 4 for the ratio (CO)(SO2) 1/2 (CO2) 1wherein the values of CO, SO2 and CO2 are the respective partialpressures.
 12. A process as described in claim 2 wherein the immisciblemetal phase is from about 5 percent to about 15 percent, by weight, ofthe molten copper sulfide.
 13. A process as described wherein more thanabout 50 percent of at least one impurity from the group consisting ofarsenic, lead, selenium, sulfur, tellurium and tin is volatilized fromthe liquid copper bath substantially saturated With oxygen.
 14. Aprocess as described in claim 2 wherein the liquid bath of coppersubstantially saturated with oxygen is treated with an atmosphere havinga reducing potential equivalent to a CO:CO2 ratio of at least about1:1000 to lower the oxygen content to less than about 0.1 percent.
 15. Aprocess as described in claim 14 wherein the atmosphere has a reducingpotential equivalent to a CO:CO2 ratio of at least about 1:50.
 16. Aprocess as described in claim 2 wherein the liquid copper containingless than about 0.1 percent oxygen is degassed and further purified by asubatmospheric pressure treatment.
 17. A process as described in claim16 wherein after degassing the liquid copper is continuously cast.
 18. Aprocess as described in claim 2 wherein the liquid copper substantiallysaturated with oxygen is subjected to a subatmospheric pressuretreatment to further lower the level of at least one impurity selectedfrom the group consisting of arsenic, bismuth, lead, selenium, sulfur,tellurium, tin and zinc before treating the liquid copper with anatmosphere reducing to cuprous oxide.
 19. A process as described inclaim 18 wherein an atmosphere reducing to cuprous oxide is passedthrough the liquid copper during the subatmospheric pressure treatmentto lower the oxygen content in the molten copper to less than about 0.1percent.
 20. A process as described in claim 18 wherein thesubatmospheric pressure is less than about 10 3 atmosphere.
 21. Aprocess as described in claim 2 wherein the steps of volatilization ofimpurities from the copper sulfide-containing bath, the production ofthe controlled amount of immiscible molten metal phase and theconverting of the copper sulfide to a molten bath of copper areconducted in a rotary furnace.
 22. A process as described in claim 2wherein the step of volatilization of impurities from the coppersulfide-containing bath is conducted at subatmospheric pressures of lessthan about 10 3 atmosphere.
 23. A process as described in claim 3wherein the precious metal concentrate from the carbonylation treatmentis leached to further concentrate the precious metals by removingcopper, sulfur and other contaminants.
 24. A process as described inclaim 3 wherein the elevated pressure during carbonylation is less thanabout 100 atmospheres.